1. Field of the Invention
The invention relates to a cleaning machine, in particular to a pass-through dishwasher, for items to be cleaned, for example dishes.
2. Description of the Background Art
Cleaning machines, in particular pass-through dishwashers, which are used, for example, to clean dishes, trays and containers which need to be cleaned having been used for communal purposes are known. Whereas dishwashers for the domestic field generally run through a program sequence comprising the successive cleaning steps with stationary arrangement of the dishes and flatware, the treatment zones in pass-through dishwashers are arranged in series and the items to be washed or cleaned are conveyed from the entry region, through the successive treatment zones which are to be passed through, to the removal region by means of suitably designed conveyor means.
Pass-through dishwashers known from the prior art have at least four treatment zones between the entry region and the exit region. A conveyor device conveys the items to be washed through the treatment zones. Said zones include a precleaning zone (preclearing area), at least one cleaning zone, a rinsing zone and a drying zone. In the precleaning zone (preclearing area), lightly adhering dirt is removed from the items to be cleaned. To this end, washing liquid is drawn from the reservoir tank associated with this treatment zone by a pump and sprayed over the items to be cleaned through suitably designed nozzles. The washing liquid then flows back into the reservoir tank again and is there again drawn up by a circulation pump and introduced into the circulation circuit. The reservoir tank is usually covered by screens in order to keep relatively large particles of dirt out of the washing liquid.
In the at least one cleaning zone which follows the precleaning zone (preclearing area), particles of dirt which are still adhering to the items to be cleaned are removed by means of a usually alkaline washing liquid. To this end, the heated washing liquid is drawn from the reservoir tank which is associated with the treatment zone by a further circulation pump and sprayed over the items to be washed by means of suitably positioned and oriented nozzles. The washing liquid then flows back into the corresponding reservoir tank again and is there drawn up by the circulation pump again. The reservoir tank is usually covered by screens in order to keep relatively coarse particles of dirt out of the washing liquid.
The generally heated washing liquid produces steam (water vapor) when it is sprayed within the respective treatment zone of the cleaning machine. In this case, it is important to keep the water vapor and therefore its energy content in this treatment zone as far as possible, in order to prevent heat energy being discharged from this zone in this way.
In the rinsing zone which follows the at least one cleaning zone, the alkaline washing liquid which wets the surface of the items to be cleaned, together with any remaining food residues, are rinsed off from the surface of the items to be cleaned by means of hot fresh water to which a rinse aid is generally added. In specific embodiments of the rinsing zone, the fresh water is once again captured in a reservoir tank associated with this treatment zone after this treatment step and drawn up by a circulation pump associated with this treatment zone and distributed over the items to be washed by means of nozzles before the actual rinsing process using fresh water. The washing liquid then flows back into the reservoir tank again and is there drawn up by the circulation pump again. The increased temperature of the heated water and the fine spraying by means of the spray nozzles likewise produce steam (water vapor) in this zone. Analogously to the at least one cleaning zone, it is likewise important here to keep the water vapor and therefore its energy content in the respective treatment zone, in this case the rinsing zone, as far as possible, in order to prevent heat energy being discharged from this zone in this way.
High-energy steam (water vapor) and moist, warm air which are conducted within the cleaning machine to at least one device for heat recovery and are then discharged from the machine are produced during the washing process in the washing liquid-bearing process steps.
In the drying zone, which follows the rinsing zone, heated air is blown onto the items which have been washed via discharge nozzles by means of a fan. The fans are designed in such a way that high air speeds can be produced at the discharge nozzle. As a result, the washing liquid which remains on the items which have been washed is removed from the items which have been cleaned partly by being blown off and partly by evaporation. Ideally, the heated air should be circulated in the drying zone and undesirable air streams toward the adjacent zone, in particular the rinsing zone and the exit region or the removal region of the cleaning machine, should be avoided. These streams can be influenced by the type of item being washed itself and the configuration of the drying zone. The air stream is usually kept within the drying zone by air-deflection troughs which are arranged within the conveyor means. The conveyor means is, for example, a continuous conveyor belt which conveys the items to be cleaned through the above-described treatment zones of the cleaning machine continuously or with the inclusion of conveying intervals.
The air stream which is discharged from the discharge nozzle of the fan strikes the air-deflection troughs, which are formed underneath the conveyor means, and divides the air stream substantially into a partial stream which is directed toward the entry region and into a partial stream which is directed toward the exit region of the cleaning machine. The usually U-shaped air-deflection trough deflects the two partial streams upward and guides them back to the fan again, in order to there be drawn up again and blown over the items which have been washed. Since the circulated air in the drying zone absorbs the moisture from the items which have been cleaned and as a result is more moist and therefore less able to absorb further moisture, some of said air has to be replaced by fresh air from the surroundings. This is achieved by a stream being generated in the direction of a suction-extraction point within the cleaning machines by suitable apparatuses, and a partial quantity of air being removed from the machine. At the same time, fresh air flows into the drying zone and replaces a portion of the air circulated in the drying zone.
DE 10 2004 003 797 A1, which corresponds to U.S. Publication No. 2007/0131260 discloses a pass-through dishwasher with a plurality of treatment zones. The flow direction of the discharge air within the cleaning machines runs from the exit to the entry, counter to the conveying direction of the items to be washed through the dishwasher, with the suction-extraction point being arranged in the area of the entry region of the dishwasher. The volumes of air which can be withdrawn from the drying zone can be changed by adjustable positioning of discharge nozzles of the fan of the drying zone.
The machines known from the prior art are designed in such a way that the air-deflection troughs and the air streams produced as a result are designed for a specific, preferably ideal, operating state. This ideal operating state is achieved only when the items to be washed, for example plates and trays, are positioned perpendicularly in the conveyor medium provided for them, the preferably employed conveyor belt, since the air conveyed by the fan can strike the air-deflection trough located beneath the conveyor medium and then guide said air back to the fan only in this state.
However, when not in the abovementioned operating state, which corresponds to the ideal operating state, special operating states are possible, in which, for example, containers, trays which are horizontal on the conveyor medium, or long, flat items to be washed, are conveyed through the various treatment zones of the pass-through dishwasher in order to be cleaned. These special operating states can occur at irregular intervals during the normal operating state. Relatively long items to be cleaned entirely or partially cover the air-deflection trough located beneath the conveyor means when the items which have been cleaned are conveyed through the drying zone. As a result, the function of the air-deflection trough, namely of circulating the air, is entirely or partly blocked. When the air stream which is discharged at high speed by the fan strikes the items which have been cleaned and are located beneath it, for example containers or horizontal trays, said air stream splits into partial streams which are directed toward the exit (point at which the items which have been cleaned are removed from the conveyor belt) and/or toward the zone adjacent to the drying area, that is to say the rinsing zone.
One partial stream, which is directed toward the rinsing area, produces an air stream through the entire pass-through dishwasher in the direction of the entry region of the cleaning machine and allows high-energy, warm and moist air and also steam (water vapor) to be discharged at the entry region. This means that the climate in the room in which the cleaning machine is installed is adversely affected since the humidity in said room increases.
The other partial stream, which is directed toward the exit region of the cleaning machine, has the disadvantageous effect that high-energy, warm, moist air flows out of the drying zone toward the removal section for the items which have been cleaned, that is to say flows into the room in which the cleaning machine is installed, and has an adverse effect on the climate of the room by increasing the humidity. In addition, water vapor, that is to say steam, can flow into the drying zone from the rinsing zone. This is accompanied by the disadvantage that a great deal of moisture is introduced into the drying zone and into the air circulating within the drying zone. This in turn leads to considerable deterioration in the drying result for the next item which has been cleaned.
The solution outlined above, which makes use of air-deflection troughs, has the disadvantage that energy is discharged from the pass-through dishwasher during temporarily occurring special operating states, for example when containers are conveyed on the preferably continuous conveyor medium or trays lie horizontal on the continuous conveyor medium, on account of the discharge of water vapor, that is to say steam. For the operator of such pass-through dishwashers, this means a resulting increased energy requirement in order to cover the energy losses. In addition, the operating personnel in the entry region, that is to say the region in which the preferably continuous conveyor medium is loaded, and in the removal region, that is to say when the items which have been cleaned are removed from the continuous conveyor medium, are subjected to increased exposure to the high-energy water vapor which is discharged.